Quickly Check Zero: Laser class IIIA, <4.5mW. Simply choose the caliber adapter for boresight and place the laser unit in the muzzle with a screwdriver. The laser bore sight kit’s multiple calibers will emit a straight Red laser beam with a long sighting range. Bore sighter for all guns allows you to quickly zero in on your target without wasting excessive amounts of ammo. Fits Calibers from .170 .22 to 12GA: Red Laser bore sighter ​with a unique system of 12 adapters fit all .170 .22 to 12GA caliber, hunting rifles, pistols/handguns, scope, could be as 9mm bore sight, 308 bore sight, 556 lasers bore sight, 12 gauge bore sight and so on. Select and adjust the proper barrel adapter, slide into the barrel and center the scope crosshairs or iron sights on the dot, just lightly press to turn ON/OFF the laser bore sighter for all guns, easier use, and control. Ultra-Long Life Battery: Our upgraded CR2 battery for this American point barrel laser bore sight kit has ultra-long battery life and longer service life than others, which can be used continuously for up to 16 hours. If the battery for laser gun sights is dead, there is no need to repurchase the battery, just use the battery charger (included), and you can continue to use a laser bore sighter 5.56.